Vulcanization of rubber



' the thiazyl ulfide ac Patented Apr. 14, 1953 VULCANIZATIQN oF RUBBER, Byron; A. Hunter, (inform and Harry D. Glenn,

' Naueanica;uteri-J;animus ti United States RubberJGompany, New York, N. Y., a corpora- Nonrawina. arnlieat sinlliasc 1,

- Eiteial: 217,066,

a. (c l- 2605a?) This invention relates to the vulcanization 9i rubber and similar sulfur -vulcanizab le unperlike materials by animproved process emp, ing

a new accelerator mix. In particulaif;lf'he,imfiyr tion relates to the use or" cl emical'ssuitable as ac s 9f. hiaz l a elera rs white known as thiazyl sulfide accelerators.

Thiazyl sulfide accelerators are widely. used inv thevulcanizati n of rubhe tthe. tire mos 01 standin examples h r e :eah qhenze hia ele and dibenzothiazyl due -r n t ua era l e ra er s. used W a chemical activator whim the ate 1 cure! T e improvement 9i; this. nv ntion v s Q911- cerned with the use of certain substituted am: monium carbamates has activators for theip ils maryacoelerator. l

- The substituted ammoniumcarbamates. are elf? fective activators of thiazyl sulfide accelerators and may be employed the. vulcanization of either natural or synthetic. rubber which i5. 1W1- canizableawith sulfur, and. therefore those syn= thetic rubbers which are; vulcanizable by sulfur are to, be considered the equivalent of natural rubber for the purposes of thejinyent-ion, vThe new activators subscribe, to the formula where R is an alkyl, cycloalkyl beta-cyanoalkyl,

aralky-l, or alk-ylene group; R beingfhydrogen, alkyl, aralkyl, or alkylene group. Exemplary of such chemical activators are:

N,N-dimethyl ammonium N,I I'-dimethyl carbamate N- ethyl ammonium '"N' rethyl carbamate N,N -diethyl ammonium N',N'-diethyl carbamate N-p opyl imnpnium N'mre rl earbemate N-i prop l amm ium N' o mpyl ar amate s bamate V N,N- 1ii o r py1 ammonium NflN' diise reprl carbamate v 2 N -ethyl-N-cyclohexylammonium N-ethyl-N'-cyclohexyl carbamate Morpholinium N -oxydiethylene carbamate Piperidinium N'-cyclopentamethylene carbamate 5 N-ethyl beta-cyanoethylammonium N-ethyl N'- beta,-cyanoethyl carbamate N ,N-dimethylammonium N-benzyl carbamate N,N:1diethyl ammonium N'-benzyl carbamate N'- 21 .1 rl ca bamate Examples of thiazyl sulfide accelerators, amongstothers, which are useful as primary ac.- celerators for purposes of theinvention, include:

Me, ea1 tobenzc2thiaZo e Zinc'salt of mercaptobenz othiaz ole l lihenzothiazy s isiilfid Y Necyclohexyl benzothiazyl sulf enamide Z-mercapto-d-ethyl thiazole 51 fl. imfil hlll lilliazyl lllflll 2c Dinit Phenn henzot a, Phenyl amino methyl Z-bengothiagyl sulfide.

Accordingly, the invention embraces a sulfurvulcanizable rubber composition c ntaining, be Qr side su1fur,'a primarythiazyl sulfide accelerator andan activator therefor, which .isa Substitut ammonium carbamate; more particularly, a car: bamate selected from the class consisting of die alkylammonium gdialkyl carbamates, monoalkylammonium monoalkyl' carbamates, monoara-lkyl ammonium monoaralkyl carbamates, cyeloale k lammeni m Q QlQa X allay; 9Y- alea ky amme i a yl eys el l; carb m dialkylammonium monoaralkyl carbamates', alkyl es e a etl y ammsi m al s beta-wa et i i eamat sl a t emmq m on a r carbamates, 'morbholinium oxy'diethylene ear:

hahlates, hi eiieil ium e qleneh amet l ha bamates The cyclohexyiamine derivative shown above 40 a pxeet ea a tae aee the ce bam tes methyl, ethyl dimethyl, h t' s n Y an end amines. .19 h' e' es a ed, has less odor; "It is also e. a tt t'et rnewt-1. cyl carb mates are also excebe v t is 9 I desirab e pr rt es, ee zpf 'eee are eselaefituted ma readily prepared by reaction of oxide on the anhydrous amines.

3 the amine. a iiteti ei her imitate (e. g., benzene; petroleum ether, chlorinated solvents, ethyl alcohol). Sufiicient solid carbon dioxide is added to convert all of the amine to the carbamate. Generally, an excess of solid carbon dioxide is used since the unreacted carbon dioxide rapidly volatilizes away. The end of the re- 30 pounds per square inch steam pressure. The stress at 300% and 500% elongation as well as the ultimate tensile (p. s. i.) strength and ultimate elongation were measured. The results are compiled in-the table.

TABLE I Stress E] ti onga on Stock Activator Amount at break 300% 500% Break A None I 630 1770 2710 630 B Cyclohexylammonium (0.3) 1590 3820 4230 556 cyclohexyl carbamate.

Dodecylammonium (0.3) 1330 3100 4010 625 dodecyl carbamate.

D Benzylammonium (0.3) 1230 3030 3990 630 benzyl carbamate.

E Isopropylammonium (0.3) 1280 2790 4050 660 isopropylcarbamate.

F Heptylammonium (0.25) 1073 2680 3980 690 heptyl carbamate.

G Octylammonium (0.25) 1125 2840 4130 675 octyl carbamate.

H Piperidinium cyclo- (0.25) 800 2190 3510 686 pentamethylene carbamate.

I Morpholinium oxy- (0.25) 890 2350 3675 686 d'iethylene carbama e.

I Diphenylguanidine.- (0.3) 1180 2930 3830 586 K Merlcaptobenzothia (0.5) 900 2480 3640 650 zo e.

action is reached when the initial exothermic reaction ceases and the solution becomes cold. The products generally separate as crystalline solids or as oils which may crystallize on standing.

Some of the substituted ammonium carbamates which appear to be new are:

Cyclohexylammonium N'-cyclohexy1 carbamate, M. P. 112--l13 C. Anal. N: Calc., 11.6%. Found, 11.35%.

Isopropylammonium N-isopropyl carbamate, M. P. 80-81 C. (sealed tube). Anal. N: Calc., 17.3%. Found, 16.9%.

Morpholinium N-oxydiethylene carbamate, M. P. 99101 C. (w/gas evolution). .Anal. N: Calc., 12.82%. Found, 12.68%, 12.63%.

Octylammonium N-octyl carbamate, M. P. 84-86 C. Anal. N: Calc., 9.26%. Found, 9.08, 9.07%.

Heptylammonium N'-hepty1 carbamate, M. F. 82-84" C. Anal. N: Calc., 10.22%. Found, 9.86, 9.96, 10.12%.

n-Propylammonium N'-n-propyl carbamate, M. P. 73-74 C. Anal. N: Calc., 17.3%. Found, 16.6%.

n-Butylammonium N'-n-butyl carbamate. M. P. 81-82 C. Anal. N: Calc., 14.7%. Found.

The following examples are given to illustrate the invention, the parts being by weight Diphenylamine-acetone reaction product (antioxidant) 1.0 Mercaptobenzothlazole 0.5

This natural rubber composition was divided into portions and these mixed with chemicals of this invention in the amounts shown in the table and the resulting stocks cured for minutes at By variation in the quantity of activators used, greater or less activation may be obtained to suit the particular need. In general, 0.1 to 1.0 part of the activator based on parts of the rubber of the thiaZole-accelerated stock should be used. The primary accelerator may be used in usual amounts, but is preferably reduced on the order of 0.1 to 1.0 part to 100 parts of rubber.

Instead of being added separately, the accelerator-activator mixed can be previously pre pared and composed of a major proportion of the thiazole accelerator and a minor proportion of the activator, and added in the form of a mixture to the vulcanizable rubber batch.

The invention may be practiced with the use of fillers, softeners, and antioxidants other than those shown in the above examples, and the rubber when compounded for curing may be either in solid form, or in the form of an emulsion or dispersion.

Having thus described our invention, What we claim and desire to protect by Letters Patent is:

1. A natural rubber composition containing sulfur sufficient to cure the rubber, a primary thiazyl sulfide accelerator, and an activator for said accelerator which is a carbamate of the formula R 0 R w ke-Na RI RI where R is a member selected from the class consisting of an alkyl, cycloalkyl, beta-cyanoalkyl, aralkyl, and alkylene group; R being a member selected from the class consisting of hydrogen, alkyl, aralkyl, and alkylene, said activator being present inan amount sufficient to activate the primary accelerator.

2. A method which comprises vulcanizing a composition containing natural rubber, sulfur sufiicient to cure the rubber,a primary thiazyl sulfide accelerator. and an activator of the formula where R is a member selected from the class consisting of an alkyl, cycloalkyl, beta-cyano alkyl, aralkyl, and alkylene group; B. being a member selected from the class consisting of hydrogen, alkyl, analkyl, and alkylene said activatcr being present in an amount suiiicient to activate the primary accelerator.

3. Cyclohexylammonium cyclohexyl carbamate.

a. Octyl ammonium octyl carbamate.

5. A vulcanization accelerator composition which is a mixture of a major proportion of thiazyl sulfide accelerator and a minor proportion of an activator for said accelerator which is a carbamate of the formula R Y o R N( -ON2 where R is an alkyl, cycloalkyl, beta-cyanoalkyl, aralkyl, or alkylene group; B. being hydrogen, alkyl, aralkyl, or alkylene group.

6. A vulcanization activator which is a carbamate selected from the group consisting of cycloheXyl-ammonium cyclohexyl carbamate, and octyl ammonium octyl carbamate.

'7. A method which comprises vulcanizing a. natural rubber composition. containing sulfur sufficient to cure the rubber, a primary thiazyl sulfide accelerator, and from about 0.1 to 1.0 part by weight (based on 100' parts by weight of the rubber) of an activator for said primary accelerator which is a carbamate of the formula Where R is a member selected from the class consisting of an alkyl, cycloalkyl, beta-cyanoalkyl, aralkyl, and alkylene group; R being a member selected from the class consisting of hydrogen, alkyl, aralkyl, and alkylene.

BYRON A. HUNTER. HARRY D. GLENN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,926,739 Clapson et a1 Sept. 12, 1933 2,222,354 Lichty Nov. 19, 1940 OTHER REFERENCES Skita et al., Ber. Deut. Chem, vol 53, pages 1242- (1920). (Copy in Sci. Lib.)

Flaschentrager et al., Z. Physiol. Chem, vol. 192, pages 268-273 (1930). (Copy in Sci. Library.) 

1. A NATURAL RUBBER COMPOSITION CONTAINING SULFUR SUFFICIENT TO CURE THE RUBBER, A PRIMARY THIAZYL SULFIDE ACCELERATOR, AND AN ACTIVATOR FOR SAID ACCELERATOR WHICH IS A CARBOMATE OF THE FORMULA 